Synopsis

The so-called 'combined tests' that the seven Dutch screening laboratories carry out for Down syndrome were carried out in line with the quality requirements in 2014 and 2015. These are the findings of an assessment by RIVM. This meets the directive of the Dutch Ministry of Health, Welfare and Sport to ensure the quality of the combined test.

Since 1 January 2007, the screening for Down syndrome has been available to all pregnant women, as part of a national screening programme. The screening for Edwards' syndrome and Patau's syndrome was added to the programme later. The screening is based on the measurements of a particular hormone and protein level, combined with an ultrasound scan measuring nuchal translucency.

A total of 58955 screening tests were carried out in 2014, plus 60422 in 2015, meaning that 33.0 and 34.7 per cent of pregnant women had combined tests carried out in 2014 and 2015 respectively. This is slightly more than in 2009-2013. The breakdown by age category shows changes in the percentages of women taking part: women aged under the age of 36 were having a test carried out more often in 2015 than in 2007-2014, whereas women aged over 36 were doing so less frequently in 2015. This may possibly be explained by the fact that the test has no longer been included since 2015 in the basic health insurance package for women aged over 36.

The laboratories perform all blood analyses. The risk calculation based on the blood analysis may be performed either by the laboratory or by some of the ultrasound scanning centres in the Netherlands. The risk calculations for 46 percent of the total number of combined tests performed in 2015 were done in the laboratories. This evaluation is only based on the probability calculation as performed by the laboratories.

The age at which the test is most frequently carried out in 2015 varies between the laboratories, with median ages ranging from 31.4 to 32.9. The number of pregnant women that have an increased risk of a child with Down syndrome varies slightly per laboratory (between 4.0 and 5.9 per cent). These differences are caused, among other things, by the average age of participating pregnant women, which differs slightly per region.